At a Glance

Male infants, boys, or young men with recurrent or chronic eczematous dermatitis; recurrent, chronic, or severe infections; thrombocytopenia with abnormal bleeding; and small platelets should be considered for the diagnosis of Wiskott-Aldrich syndrome (WAS). Thrombocytopenia with bleeding is frequently present immediately after birth, and any male with thrombocytopenia and small platelets should be tested for WAS. Infections associated with WAS include otitis or sinopulmonary infections, meningitis, and pneumocystis pneumonia. Boys with chronic thrombocytopenia or neutropenia may have limited forms of WAS.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Platelet counts and evaluation of platelet volume are helpful, since thrombocytopenia is present in most patients. Lymphocyte counts are usually normal at birth, but lymphopenia may develop by 6 years of age. Flow cytometry to evaluate T-cell number can be helpful. Immunoglobulin serum concentrations should be measured. Total IgG and IgM levels are usually normal or somewhat low, whereas total IgE and IgA are usually elevated. After immunization with carbohydrate antigens (such as Pneumovax), antibodies to carbohydrate antigens fail to develop and the antibody response to protein antigens (e.g., tetanus and diphtheria) is often below normal. Selected IgG antibodies should be measured after immunization; a subnormal antibody response would support the diagnosis of WAS.

In suspected cases, flow cytometry should be performed on peripheral blood leukocytes to assess the presence of the Wiskott-Aldrich syndrome protein (WASP). Absence of the WASP in peripheral blood lymphocytes establishes the diagnosis. (Table 1)

Table 1.

Test Results Indicative of the Disorder

Platelet Count

IgG Serum Concentration

Flow Cytometry of WASP

30,000 with small platelets

600 mg/dL (low end of normal)

Subnormal

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Many different drugs and condition can cause thrombocytopenia, immunodeficiency syndromes, etc.

What Lab Results Are Absolutely Confirmatory?

Determining the DNA sequence of the WASP gene to identify the genetic abnormality in the WASP gene is definitive.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Many different mutations in the WASP gene have been described. A mild form of WASP gene mutation causes X-linked thrombocytopenia in which patients have chronic thrombocytopenia with minimal or no eczema or immune deficiency.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Common autoimmune features include autoimmune hemolytic anemia, vasculitis (including Henoch-Schonlein deficiency), and inflammatory bowel disease. Patients with these associated conditions will also have the abnormal tests associated with those conditions.